1. Field of the Invention
The present invention relates to a method of forming a phosphor screen for use with a cathode ray tube, such as a projector tube or the like, for example.
2. Description of the Prior Art
There has hitherto been proposed a method of forming a lacquer film layer to form a phosphor screen of this kind of cathode ray tube. According to the conventional method, as shown in FIGS. 1 and 2, on a phosphor layer 11 formed on the inner surface of a glass panel 10 is formed a film layer 12 by coating and vapor-depositing an intermediate film layer solution which will be described later on. This film layer 12 will be referred to hereinafter as "intermediate solution film layer 12". Then, a lacquer film layer 13 is formed on the intermediate solution film layer 12 by coating, evaporating and drying the lacquer, and an aluminum layer (metal-backing layer) 14 is formed on the lacquer film layer 13 by vapor deposition. Further, the intermediate solution film layer 12 and the lacquer film layer 13 are thermally decomposed by baking.
The above-mentioned method, however, encountered with the following problems.
Specifically, as shown in FIG. 2, the intermediate solution film layer 12 and the lacquer film layer 13 are formed on the inner surface of a so-called skirt portion of the very smooth panel 10. Then, the aluminum layer 14 is formed on the lacquer film layer 13. The aluminum layer 14 that was formed on the skirt portion 10a tends to become nonuniform because gas that was generated in the baking process cannot be escaped from the aluminum layer 14. There is then the risk that the aluminum layer 14 formed on the effective picture screen portion of the phosphor panel will be damaged.
To solve this problem, it has hitherto been proposed to remove the lacquer film (the intermediate solution film layer 12 and the lacquer film layer 13) by workers before aluminum is deposited on the skirt portion of the panel 10 by vapor deposition (see FIGS. 3A and 3B).
However, it is not possible to stably remove the lacquer films formed on the panel 10 by hands. In particular, it is very difficult to wipe out a border between the glass surfaces of the phosphor layer 11 and the panel 10. Thus, it is frequently observed that the border between the phosphor layer 11 and the glass surface is wiped out in a wrong manner. As a consequence, the quality of the phosphor screen and the yield of the phosphor screen are deteriorated and the number of workers required when the phosphor screen is produced is increased. Therefore, the phosphor screen becomes expensive.
Furthermore, it is proposed to form the lacquer layer on the inner surface of the panel 10 only at its portion where the phosphor layer 11 is formed. In that case, there is then the problem that the production installation required when phosphor screens are produced becomes complicated.